1. Field of the Invention
The present invention relates to a dome type diaphragm and a loudspeaker apparatus.
2. Description of the Related Art
Conventionally, the dome type diaphragm has been widely employed in the loudspeaker apparatus for reproduction of middle and high pitched sound (e.g., refer to JP-A-2-312396).
FIG. 1 shows a conventional example of the loudspeaker apparatus having the dome type diaphragm.
The loudspeaker apparatus 1 as shown here has a top plate 5 composed of a disk-like magnetic substance provided in front (upwards in FIG. 1) of a disk-like magnet (permanent magnet) 4, and a barrel-type yoke 6 provided from the rear to front part of the magnet 4 to constitute a magnetic circuit of inner magnetization type, with a magnetic gap 10 being formed between the outer circumference of the top plate 5 and the inner circumference in front of the barrel-type yoke 6.
Also, a voice coil 7 having the windings 12 wound around the outer peripheral face in the rear of a cylindrical bobbin 8 is covered over the front opening end portion around which the dome type diaphragm 11 is fitted, with an annular edge (edge member) 9 provided around its outer circumference.
And the voice coil 7 has a rear opening end portion of the bobbin 8 disposed in the magnetic gap 10 so that the windings 12 maybe located in the magnetic gap 10, and an outer peripheral portion of the edge 9 is fixed to the frame 2. Thus, the voice coil 7 is held via the edge 9 in the frame 2 freely vibratingly.
The dome type diaphragm 11 is formed like a dome type from a metal thin plate of aluminum alloy or the like, with a flat reinforcing portion 11a extending horizontally on its outer peripheral edge. That is, the flat reinforcing portion 11a is disposed to extend on the outer peripheral edge of the metal thin plate formed like the dome type to secure the mechanical strength of the dome type diaphragm 11 and improve the high frequency characteristics of the loudspeaker apparatus 1.
Moreover, each end of the windings 12 wound around the bobbin 8 is connected via a connection portion provided on the outer peripheral face of the bobbin 8 to one end of the lead wire 14, the other end of the lead wire 14 being connected to a terminal 16 of a connector portion 20 molded integrally with the frame 2.
A cover 3 mounted on the frame 2 is placed above the dome type diaphragm 11. This cover 3 protects the dome type diaphragm 11 from a physical external force, and appropriately radiates the sound produced by the dome type diaphragm 11 through a plurality of sound radiating holes.
Thus, if a signal current is supplied to the windings 12 connected to an amplifier via a connection cable of the other connector (not shown) fitted into the connector portion 20 and the lead wire 14, the dome type diaphragm 11 is vibrated along with the voice coil 7 to output the sound.
However, when the flat reinforcing portion 11a is disposed to extend around the outer peripheral edge of the dome type diaphragm 11 as described above, there is the possibility that the flat reinforcing portion 11a may interfere with a curved portion 9a of the edge 9, or the lead wire 14 disposed on the front face of the edge 9 and the metallic flat reinforcing portion 11a may be contacted and short-circuited, whereby it is required that the height H1 of the bobbin 8 in the bobbin coil 7 is increased to keep a clearance between the edge 9 and the flat reinforcing portion 11a. 
Thus, the voice coil 7 with the height H1 increased has a problem that the rigidity is reduced to cause a transmission loss, and the weight is increased to attenuate the high frequency characteristics.